About 25 different kinds of fish could be seen under the 250-meter (820-foot) - long ice circuit. The park in the city of Kitakyushu opened the "Ice Aquarium" as an "attraction never heard about" earlier this month.

Space World said that the fish were intended "to give the feel of the ocean to the ice skating rink," and that the amusement park is "extremely remorseful to have invoked such unpleasant feelings."

According to CNBC, Japanese broadcaster NHK showed the fish frozen in ice on a blue floor and some formed a school to spell out "HELLO" or make an arrow-shaped sign in the ice.

The amusement park plans to hold a memorial service for the fish once they are taken out of the ice.

"Space World said the fish were purchased from a fish market, and were dead before the water was frozen," CNBC reports.